Floppy magnetic recording discs are flexible discs of polyester resin or the like having a magnetic layer on each side thereof on which information is recorded by a magnetic head. Floppy discs which have a diameter of 31/2 inches (8.9 cm) or less are known as micro-floppy discs. Generally, the micro-floppy disc is accommodated in a hard casing to form a cartridge. The micro-floppy disc comprises a circular magnetic recording medium which is thin, has a small diameter, and has a hub fixed to the center of the recording medium.
A conventional micro-floppy magnetic recording disc cartridge according to the prior art is shown in FIG. 1. Cartridge 10 is comprised of a cover casing 12 and a back casing 20 which enclose a floppy magnetic recording disc 16 between them. Recording disc 16 has a metal hub 15 provided therein. Casings 12 and 20 each have a fabric liner 14 and 18, respectively, on their inner surface which approximates the shape of the disc 16. A rectangular opening 26 in cover 12 and a similar opening (not shown) in back casing 20 allows for a read/write head (not shown) to access disc 16 when the shutter (not shown) is moved to an "open" position. A centrally located circular hole 24 in back casing 20 allows for a drive mechanism (not shown) to engage hub 15 and cause disc 16 to rotate within cartridge 10.
The inner surface 34 of cover casing 12 (i.e., the surface facing disc 16) is shown in FIG. 2. A centrally located circular rib 36 is configured to maintain hub 15 therein, thereby minimizing vibration and rattle of the hub and disc 16 within cartridge 10.
An abrasion chip 38 is attached to inner surface 34 of cover casing 12 in the center of the area bounded by circular rib 36. When cartridge 10 is inserted into a drive for reading and/or writing on disc 16, a drive pin from the drive (not shown) is inserted into a centrally-located hole (not shown) within hub 15. Abrasion chip 38 prevents direct contact of the drive pin with inner surface 34 of cover casing 12 when reading and writing data on disc 16 in order to prevent abrasion of the inner surface of the cover casing. Abrasion chip 38 may be any shape, including a circle, square, rectangle, parallelogram, trapezoid, triangle, or other polygons. Abrasion chip 38 is typically affixed to inner surface 34 of cover casing 12 by an adhesive.